What is Histamine Toxicity?
Histamine toxicity, also known as scombroid poisoning, is the main type of sickness caused by eating tainted fish in the United States. Another common type is ciguatera poisoning. Interestingly, this can also happen if you eat spoiled Swiss cheese. The symptoms of this type of food poisoning often look a lot like the body’s natural response to histamine – a chemical that your immune system makes. This includes redness in your face and neck (like a flush), diarrhea, skin rash known as urticarial rash, and headaches. Rarely, some people may experience severe breathing troubles or heart issues. This usually happens in those who already have medical conditions like asthma or serious heart disease.
What Causes Histamine Toxicity?
Scombroid poisoning is a type of food poisoning that you can get from eating certain types of fish that haven’t been properly stored after they were caught. The main thing that causes this is a substance in the fish called histidine. Histidine is usually found in the dark meat of fish. If the fish gets too warm (above 4 degrees Celsius), it causes the fish to develop too many bacteria. These bacteria turn the histidine into something called histamine. If a fish is stored properly, the level of histamine is usually less than 0.1 mg per 100 g of fish. But in a fish that’s gone bad, the histamine level can be at least 20 to 50 times higher.
Most commonly, the types of bacteria responsible are Escherichia coli, Vibrio, Proteus, Klebsiella, Clostridium, Salmonella, and Shigella. Unfortunately, there’s no reliable way to tell if a fish is contaminated with these bacteria just by smelling it or looking at it. Sometimes, people do notice a honeycomb-like look to the skin of the fish after it’s cooked, or might describe eating the fish as having a “peppery” taste, but these signs are not always present.
Similarly, people have sometimes gotten sick from eating Swiss cheese because of bacterial contamination. If the milk used to make the cheese is contaminated before it’s processed, and the cheese isn’t heated up enough to kill the bacteria or stored properly afterwards, the bacteria can convert histidine to histamine. This is the same process that occurs in fish, and it can also lead to histamine toxicity.
Risk Factors and Frequency for Histamine Toxicity
People often get histamine toxicity, also known as scombroid poisoning, from eating certain types of dark meat fish. It’s often associated with fish from the Scombridae and Scomberosocidae families, which include species like tuna, mackerel, bonito, and skip-jack. In developed countries, incidents of this poisoning are more common from fish that were caught for fun rather than fish harvested for commercial use. This is due to strict rules for commercial fishing. However, it’s not just those fish that can cause the issue. Other fish like amberjack, bluefish, mahi-mahi, sardine, yellowtail, and herring can also be the culprit. In rare cases, even some contaminated Swiss cheese can trigger a reaction.
- People can get histamine toxicity, or scombroid poisoning, from eating certain types of dark meat fish.
- This often includes fish from the Scombridae and Scomberosocidae families like tuna, mackerel, bonito, and skip-jack.
- This type of poisoning is more common from recreationally caught fish in developed countries, due to strict rules for commercial fishing.
- But other fish species like amberjack, bluefish, mahi-mahi, sardine, yellowtail, and herring can cause the same issue.
- Even some contaminated Swiss cheese can cause these reactions, but this is rare.
Signs and Symptoms of Histamine Toxicity
When a fish is contaminated, it might still smell and look fresh. However, some people have reported a “peppery” taste. When you cook this fish, the skin could take on a honeycomb-like appearance.
Signs and symptoms of Scombroid poisoning often appear within two hours after eating contaminated fish. These symptoms usually last for about 12 to 48 hours. Here are some common and less common symptoms one may experience:
- Rash
- Flushing or reddening of the skin
- Headache
- Diarrhea
- Abdominal cramps
- Blurred vision
- Feeling cold
- Dizziness
- Nausea
- Sweating
- Fast heart rate (tachycardia)
In severe cases, the reactions could lead to:
- Swelling under the skin (angioedema)
- Swelling of the tongue
- Difficulty breathing
- Cardiac arrest
- Death
Note that people who are taking medications like isoniazid or monoamine oxidase inhibitors could have worse reactions due to a blockage in the digestive tract.
Testing for Histamine Toxicity
If you ate a fish meal and experienced sudden symptoms within an hour, you might be dealing with a certain health condition. These symptoms can include a sudden rush of heat (flushing), skin rash, headache, and diarrhea. If others who ate the same dish also have these symptoms, this could be further evidence of the diagnosis.
These symptoms usually improve quickly after taking an antihistamine, which is a type of medication that stops allergic reactions.
To confirm the diagnosis, your doctor may check for high levels of a substance called histamine in leftover portions of the fish you ate, or through a urine test that can measure histamine levels in your body.
Treatment Options for Histamine Toxicity
Treatment for this condition generally revolves around helping to manage symptoms. Antihistamines, which can counteract the effects of histamine produced during allergic reactions, are often used as a standard treatment. For more severe cases, other medications like steroids, beta-2-adrenergic agonists, ipratropium bromide, and epinephrine might be brought into the mix.
If a patient is experiencing constriction of the airways (bronchospasm), swelling in the airway (airway edema), or a type of severe low blood pressure that can lead to organ damage (distributive shock), their situation may be treated similarly to anaphylaxis. In these cases, epinephrine, which can rapidly reduce allergic symptoms, is commonly administered.
What else can Histamine Toxicity be?
If you have symptoms like an allergic reaction to fish, even though you’ve never been allergic before, it could be a sign of something called ‘scombroid’. This is even more likely if other people who ate the same fish are also showing symptoms.
These symptoms can sometimes be mistaken for other medical conditions. For example, the sweating, nausea, chest tightness and difficulty breathing can feel a lot like a heart attack, or ‘myocardial ischemia’.
Another condition it can be confused with is food poisoning, especially the kind caused by a bacteria called Staphylococcus aureus. This causes similar symptoms of sudden nausea, vomiting, and abdominal pain within 2 hours of eating contaminated food. However, these patients might also develop a fever, which doesn’t happen with scombroid. And people with scombroid usually have a rash or flushed skin, which doesn’t happen with this type of food poisoning.
Also, other types of food poisoning from seafood – like ciguatera, shellfish, and pufferfish – can mimic scombroid. But these don’t typically show up right away like scombroid does, and they don’t cause the same histamine reactions, like skin flushing and a rash.
What to expect with Histamine Toxicity
The outlook for most patients is quite positive. Many see quick improvement with the use of specific medications, known as H1 and/or H2 antihistamines (like diphenhydramine and/or cimetidine or ranitidine).
Remarkably, even patients showing severe symptoms often get better within a few hours after receiving treatment.
Possible Complications When Diagnosed with Histamine Toxicity
Most complications are unusual, and patients often quickly get better with treatment, typically not needing any further follow-ups. Most of them can be sent home after treatment. However, patients with severe bronchospasm (tightness in the chest), signs of shock, or irregular heart rhythms might require monitoring for up to 24 hours. Even those with severe symptoms generally improve quickly when given antihistamines within a few hours of treatment, and they can usually go home afterwards.
Common Outcome Situations:
- Most complications are infrequent
- Patients often improve rapidly with treatment
- No need for further follow-up for most patients
- Most patients can be discharged home
- Patients with severe bronchospasm, signs of shock, or irregular heart rhythms may require monitoring for up to 24 hours
- Quick improvement of severe symptoms with antihistamines within hours of treatment
- Even severely symptomatic patients can usually be discharged home after treatment
Preventing Histamine Toxicity
It’s important to educate patients, especially those who enjoy recreational fishing, on the correct way to store fish before eating it. Please do note that getting sick from poorly stored fish does not necessarily mean that a person is allergic to fish.
